Liquefied natural gas (LNG) is increasingly being considered as a fuel for locomotive engines. LNG is a gaseous fuel that is defined herein as any fuel that is in a gas state at standard temperature and pressure, which for the purpose of this disclosure is defined as 20 degrees Celsius (° C.) and 1 atmosphere (atm) respectively. A gaseous fuel may also be referred to as a gas in this disclosure. Emissions can be reduced and the cost of fuelling lowered when these engines are fuelled with LNG compared to being fuelled with diesel.
In conventionally fuelled locomotives, diesel is stored in tanks that are located on the locomotive. A locomotive engine controller controls a fuel pump that delivers diesel at predetermined pressures to the engine. In locomotives that fuel with LNG, the liquefied gaseous fuel is stored in specially constructed tanks on a tender car connected with the locomotive. In applications that require more power than one locomotive can provide, or more fuel than one tender car can provide, one or more tender cars can store gaseous fuel for one or more locomotives.
The delivery of gaseous fuel from the tender car to the locomotive engine is inherently more complicated compared to delivering diesel fuel, for a variety of reasons. There can be delays in delivering gaseous fuel to the locomotive due to start-up delays for a cryogenic pump that must be cooled before it can efficiently pump liquefied gaseous fuel. Gaseous fuel is delivered from a tender car that is detachable from the locomotive. Safety issues must be taken into consideration to ensure that gaseous fuel does not escape the fuelling system in the event the tender car separates from the locomotive. The distance traveled by the gaseous fuel between where it is stored and where it is combusted is considerably greater, which has the potential to further adversely affect start-up delays and increases the likelihood of gaseous fuel venting after shut-down. Normally, the gaseous fuel is converted from the liquid state to the gas or supercritical state before it is introduced to either the intake system or combustion chambers of the locomotive engine. Gaseous fuel pressure and temperature are regulated such that fuel injection metering can be controlled. This comprises controlling the cryogenic pump to maintain the pressure of the fuel within predetermined ranges, and to ensure the temperature of the fuel delivered to the engine is above a predetermined minimum value such that fuel system components are not damaged and to prevent freezing.
U.S. Pat. No. 5,887,567, issued Mar. 30, 1999 to White et al. (hereinafter White), discloses a natural gas fuelling system for cryogenic fluids between a container of fuel carried on a flat car and a locomotive. Two configurations for delivering LNG from the container to the locomotive are disclosed. In a first configuration a control system on a skid frame located on the flat car delivers vaporized gaseous fuel to the locomotive. The control system comprises one or more pumps, meters, controls and vaporizers. In a second configuration, liquid LNG is supplied to combustion chambers of the locomotive engine. Nowhere does White disclose how the control system functions over the many operational states of both the locomotive engine and the tender car.
The state of the art is lacking in techniques for managing a supply of gaseous fuel on a tender car during the various operational modes of the tender car. The present method and apparatus provides an improved technique for managing supplies of gaseous fuel on tender cars.